When the countersunk part of a hole is formed, it will accommodate the head of a fastener, such as a rivet or screw, having a shank portion from which extends a terminal or head portion flaring angularly outward from the shank portion. Thus, in the countersunk part of the hole, the outwardly flaring portion engages the head portion of the fastener.
Conventional countersink tools include a rotating shaft, with the cutting edges constituting an integral part thereof. However, this type of countersink tool has a relatively large initial expense when comparing the cost of the countersink tool to the number of holes that it will countersink before the integral edges on the tool wear out. Moreover, when the integral edges on a conventional countersink tool wear out, the entire countersink tool must be subjected to a regrinding operation which is a relatively complicated, time-consuming and an expensive operation. This regrinding operation must be performed on a special machine which can accommodate the entire countersink tool. The regrinding operation was necessary, however, because the large initial expense of the countersink tool made it too expensive to throw it away after it wore down. Furthermore, the cutting edges on an integral countersink tool can be reground only a limited number of times. Eventually, the edges cannot be reground, and, thus, the entire tool must be thrown away and replaced.
Other countersink tools having removable countersink inserts have been used to countersink relatively large holes. Because of the large size of these holes, and thus the large size of the countersink holders, multiple fluted tools are used. However, when countersinking smaller size holes, the holder becomes smaller and it is impossible to machine numerous cutaways or pockets in the cutting holder to accommodate multiple cutting inserts.